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The growing interest in nanomaterials in different application fields calls for the implementation of simple, economically appealing, and efficient preparative methods. Among the wide variety of nanomaterials, carbon nanostructures have a special place due to their potential technological applications. Here, we present a fast, cheap, and easy-to-implement microwaveassisted method for the preparation of carbon nanotubes (CNTs) and carbon fibers (CFs) at room pressure conditions. The synthesis involves heating a mixture of graphite and ferrocene contained in a simple glass tube using a conventional microwave oven. A mixture of multi-walled carbon nanotubes (MWCNTs) and [Fe.sub.3][O.sub.4] magnetic nanoparticles were obtained quickly (less than 30 s) and in good yields. The products were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), and Raman spectroscopy. Key words: nanomaterials, multi-walled carbon nanotube (MWCNT), microwave synthesis, carbon nanostructures. L'interet grandissant pour les nanomateriaux dans differents champs d'application constitue un motif pour la mise au point de procedes simples, economiques et efficaces pour les fabriquer. Parmi la grande variete de nanomateriaux, les nanostructures de carbone occupent une place particuliere en raison de leurs possibles applications technologiques. Dans le present article, nous presentons un procede assiste par microondes pour la synthese de nanotubes de carbone (NTC) et de fibres de carbone (FC) a pression atmospherique qui est rapide, economique et facile a mettre en ceuvre. La synthese consiste a chauffer un melange de graphite et de ferrocene dans une simple eprouvette de verre au moyen d'un four a microonde de cuisine. Nous avons obtenu un melange de nanotubes de carbone a parois multiples (NTCPM) et de nanoparticules de [Fe.sub.3][O.sub.4] magnetiques, et ce, rapidement (moins de 30 secondes) et avec de bons rendements. Nous avons caracterise les produits par microscopie electronique a balayage (MEB), microscopie electronique en transmission (MET), diffraction des rayons X (DRX) sur poudre et spectroscopie Raman. [Traduit par la Redaction] Mots-cles: nanomateriaux, NTCPM, synthese par microondes, nanostructures de carbone., Introduction Carbon is a remarkable element that can be considered as the key element of living entities. Thanks to its ability to bond to itself forming oligomers and polymers, it [...]

Objective. Dexamethasone is used in very low birth weight (VLBW) ventilator-dependent infants to prevent or decrease the severity of chronic lung disease. We reported a significant increase in respiratory compliance during a 7-day weaning course of moderately early dexamethasone therapy (0.5 mg/kg/d) in VLBW infants, along with a shorter duration of mechanical ventilation and [O.sub.2] supplementation. Although 0.5 mg/kg/d has been the most commonly used dose in preterm infants, the use of a lower dose of dexamethasone may reduce potential adverse effects of steroid therapy. Quantification of dynamic pulmonary mechanics in VLBW infants who receive low-dose dexamethasone has not been reported. The objective of this study was to compare the effect of 2 dose regimens of dexamethasone on dynamic pulmonary mechanics, mean airway pressure (MAP), and fractional inspired oxygen concentration (FI[O.sub.2]) in intubated VLBW infants who were at risk for chronic lung disease. Methods. We studied 47 VLBW (birth weight: 550-1290 g; gestational age: 24-30 weeks) ventilator-dependent infants at 7 to 14 days of age. Twenty-three infants were randomized to receive dexamethasone at 0.5 mg/ kg/d intravenously for 3 days (high dose), 0.25 mg/kg/d for 3 days, and 0.1 mg/kg/d during the 7th day; 24 infants received low-dose dexamethasone as 0.2 mg/kg/d for 3 days and 0.1 mg/kg/d for 4 days. Respiratory compliance (Crs) and resistance were measured before and on days 2, 5, and 7 of dexamethasone therapy. We recorded airway pressure, flow, and tidal volume, and mechanical breaths were analyzed. Results. Crs significantly increased during dexamethasone therapy in both groups of infants when compared with baseline (74% increase in the high-dose group and 66% increase in the low-dose group). Dexamethasone increased tidal volume and significantly reduced FI[O.sub.2] and MAP in both groups of infants. A transient increase in blood pressure was noted in both groups. Conclusions. Our findings indicate that 1) comparable significant increases in Crs are present in the low-dose dexamethasone as well as the high-dose dexamethasone groups on days 2, 5, and 7 of steroid therapy; and 2) MAP and FI[O.sub.2] are significantly decreased during dexamethasone therapy in both groups of infants. We conclude that low-dose and high-dose dexamethasone, as used in this study, have comparable beneficial effects on dynamic pulmonary mechanics and subsequently on oxygen requirement and applied ventilatory support in VLBW infants. Pediatrics 2002;109:262-268; low-dose dexamethasone, very low birth weight infants, dynamic respiratory compliance, oxygenation, mean airway pressure., ABBREVIATIONS. CLD, chronic lung disease; VLBW, very low birth weight; Crs, dynamic respiratory system compliance; MAP, mean airway pressure; FI[O.sub.2], fractional inspired oxygen concentration; IVH, intraventricular hemorrhage; Rrs, dynamic respiratory [...]

1 Optimal dipeptide and peptidomimetic drug transport across the intestinal mucosal surface is dependent upon the co-operative functional activity of the di/tripeptide transporter hPepT1 and the Na[sup +]/H[sup -] exchanger NHE3. The ability of the anti-absorptive enteric neuropeptide VIP (vasoactive intestinal peptide) to modulate dipeptide uptake was determined using human intestinal (Caco-2) epithelial cell monolayers. 2 Uptake of glycylsarcosine (Gly-Sar) across the apical membrane of Caco-2 cell monolayers is inhibited by basolateral exposure to either VIP, pituitary adenylate cyclase-activating polypeptide (PACAP), or the VPAC[sub 1] receptor agonist [[sup 11,22,28]Ala]-VIP. Inhibition of Gly-Sar uptake is observed only in the presence of extracellular Na[sup +]. Reverse-transcription polymerase chain reaction (RTPCR) demonstrates that VPAC[sub 1] mRNA is expressed in Caco-2 cells whereas VPAC[sub 2] mRNA is not detected. 3 The VIP-induced inhibition of Gly-Sar uptake is abolished in the presence of the protein kinase A (PKA) inhibitor H-89 (N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide.2HCl). 4 [sup 22]Na[sup +] uptake across the apical membrane is inhibited by the selective NHE3 inhibitor S1611. Experiments with BCECF [2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein]-loaded Caco-2 cells demonstrate that VIP reduces the NHE3-dependent recovery of intracellular pH (pH[sub i]) after dipeptide-induced acidification. Western blot of Caco-2 cell protein demonstrates expression of the NHE regulatory factor NHERF1 (expression of which is thought to be required for PKA-mediated inhibition of NHE3). 5 VIP has no effect on Gly-Sar uptake in the presence of S1611 suggesting that VIP and S1611 both modulate dipeptide uptake via the same mechanism. 6 These observations demonstrate that VIP (and PACAP) modulate activity of the H[sup +]/dipeptide transporter hPepT1 in a Na[sup +]-dependent manner consistent with the modulation being indirect through... [ABSTRACT FROM AUTHOR]